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Öğe Band offsets, dielectric dispersion and some applications of CdSe/GeO2 heterojunctions(Elsevier GmbH, 2021) Khusayfan, Najla M.; Qasrawi, Atef Fayez; Alharbi, S. R.; Khanfar, Hazem K.; Kayed, T. S.Herein, the formation, structural, morphological, compositional, optical, dielectric, photoelectrical and electrical properties of the CdSe/GeO2 heterojunctions are explored. While the surface displayed formation of deficient GeO, the bulk of the films exhibited correct stoichiometry of GeO2 and CdSe. It is found that stacking of GeO2 onto CdSe enhances the crystallinity of CdSe by reducing the defects concentrations. It blue shifts the energy band gap of CdSe from 1.74 eV to 2.60 eV. The stacked layers of CdSe/GeO2 displayed conduction and valence band offsets of 2.34 eV and 1.23 eV, respectively. In addition, the Drude-Lorentz model analyses have shown that the coating of GeO2 onto CdSe, highly increases the drift mobility of charge carriers and tunes the plasmon frequency making it more appropriate for optoelectronic device applications. When exposed to light irradiation, an illumination intensity dependent photosensitivity is observed. The photoconduction mechanism is governed by the sublinear recombination with exponential trap distribution. Moreover, the capacitance –voltage characteristics of the device revealed metal-oxide-semiconductor field effect transistors (MOSFET) characteristics. The built in potential for this device under reverse biasing conditions reached 4.74 eV.Öğe Characterization of PbWO4 thin films formed by the pulsed laser welding technique(Elsevier, 2023) Alfhai, Latifa Hama Khalid; Qasrawi, Atef Fayez; Khanfar, Hazem K.within couple of seconds in an argon atmosphere. Thin films of Pb (100 nm)/WO3 (500 nm) were deposited by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. The films were then exposed to a pulse laser beam of fixed amplitude and variable pulse width (0.1–10 ms). The produced films were characterized by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and optical spectrophotometry techniques. An almost pure phase (~90%) of tetragonal PbWO4 was achieved after the pulse width exceeds 5.0 ms. PbWO4 thin films produced by the PLW technique exhibited a direct and indirect energy band gaps of 2.27 eV and 3.52 eV, respectively. Energy band tails of widths of 1.35 eV were found dominant in these films. In addition fitting of the dielectric resonance spectra for Pb/WO3 and PbWO4 thin films indicated that the formation of PbWO4 was accompanied with a decrease in the high frequency dielectric constant, a decrease in the free hole concentration and an increase in the electronic friction in the films. The fast method of obtaining PbWO4 thin films and the formation of the direct band gap being 2.27 eV together with the nonlinear dielectric and optical properties make the PbWO4 films obtained by the PLW technique suitable for optoelectronic technologyÖğe Enhanced structural, optical and electrical properties of polycrystalline WO3 thin films achieved by aluminum nanosheets coating(Iop Publishing Ltd, 2024) Qasrawi, A. F.; Khanfar, Hazem K.Herein the effects of aluminum nanosheets on the structural, morphological, optical and electrical properties of tungsten oxide thin films are reported. Polycrystalline phase of the thermally evaporated WO3 was achieved by the pulsed laser welding technique. The polycrystalline films are then coated with Al nanosheets of thicknesses of 100 nm and 150 nm by the ion coating technique. It is observed that Al induces the domination of the hexagonal structure of WO3 over the tetragonal. Associated with the enhanced crystallinity the light absorption in the films increased by more than 60% and the energy band gap narrowed significantly. Namely the energy band gap of the as grown WO3 decreased from 3.15 eV to 2.85 eV and 2.59 eV as the Al layer thickness increased from 100 to 150 nm, respectively. It is also observed that crystalline films of WO3 exhibited lower electrical resistivity compared to films fabricated by other techniques. The temperature dependent electrical resistivity measurement was carried out in the temperature range of 310-420 K. It showed room temperature values of 2.5 ( Omega cm), 2.2 ( Omega cm) and 1.9 ( omega cm) and impurity levels centered at 0.25 eV, 0.34 eV and 0.16 eV for uncoated and films coated with Al nanosheets of thicknesses of 100 nm and 150 nm, respectively. The enhanced crystallinity that is accompanied with narrower energy band gap and lower electrical resistivity values make crystalline WO3 films promising for optoelectronic applications.Öğe Fast crystallization of InSe thin films via pulsed laser welding technique and effect of crystallinity on the optical and dielectric properties(IOP Publishing, 2024) Khusayfan, Najla M.; Qasrawi, Atef Fayez; Khanfar, Hazem K.; Alharbi, Seham R.Physica Scripta Inclusive Publishing Trusted Science, find out more. ACCEPTED MANUSCRIPT Fast crystallization of InSe thin films via pulsed laser welding technique and effect of crystallinity on the optical and dielectric properties Najla M. Khusayfan1, A F Qasrawi2, Hazem Khanfar3 and Seham Alharbi4 Accepted Manuscript online 18 January 2024 • © 2024 IOP Publishing Ltd What is an Accepted Manuscript? DOI 10.1088/1402-4896/ad2040 DownloadAccepted Manuscript PDF Download PDF Article metrics 3 Total downloads Submit Submit to this Journal MathJax Turn on MathJax Permissions Get permission to re-use this article Share this article Share this content via email Share on Facebook (opens new window) Share on Twitter (opens new window) Share on Mendeley (opens new window) Hide article and author information Author e-mails atef.qasrawi@aaup.edu Author affiliations 1 Department of Physics, University of Jeddah, Jeddah, Jeddah, Makkah, 21959 , SAUDI ARABIA 2 Physics Department, Arab American University, Telfit,, Jenin, P298, Palestine, State of 3 Computer system Engineering , Arab American University, Telfit,, Jenin, Jenin, P298, Palestine, State of 4 Physics Department, University of Jeddah, jeddah, Jeddah, Makkah, 21959 , SAUDI ARABIA ORCID iDs A F Qasrawi https://orcid.org/0000-0001-8193-6975 Hazem Khanfar https://orcid.org/0000-0002-3015-4049 Dates Received 5 October 2023 Revised 17 December 2023 Accepted 18 January 2024 Accepted Manuscript online 18 January 2024 Journal RSS Sign up for new issue notifications Abstract In the current study the crystalline phase of indium selenide thin films which were grown by the thermal evaporation technique is achieved via pulsed laser welding technique (PLW) in a second. The films crystallinity is achieved under various welding conditions including the pulse width (PW), repetition frequency (f_r ) and pulse diameter (d). The optimum parameters for obtaining well crystalline phase are PW=1.0 ms, f_r=10Hz and d=1.0 mm. PLW induced crystallinity showed preferred structure relating to monoclinic phase of InSe. Compositionally while amorphous films exhibited In2Se3 chemical structure, crystalline ones preferred InSe phase. Associated with this type of crystallinity, direct and indirect energy band gap values of 2.32 eV and 3.12 eV are determined. The crystalline films showed lower dielectric constant value accompanied with higher optical conductivity and higher terahertz cutoff frequency in the infrared range of light. In addition the dielectric dispersion spectra were treated using Drude-Lorentz model to read the optical conductivity parameters for the PLW assisted crystalline InSe terahertz resonators. The treatment showed that the crystallinity of the films resulted in improved free carrier density, longer relaxation times at femtosecond level, larger plasmon frequencies and higher drift mobility values. These features together with the response of terahertz cutoff frequency to IR excitations make crystalline InSe thin films promising for optoelectronic and terahertz technology applications.Öğe Growth and characterization of lanthanum germanide thin films by the thermal evaporation technique(Wiley, 2023) Alkhamisi, Manal M.; Qasrawi, Atef Fayez; Khanfar, Hazem K.Lanthanum germanide (La6Ge) thin films are successfully fabricated using the thermal evaporation technique under a vacuum pressure of 10?5 mbar. The resulting films display an orthorhombic structure, characterized by lattice parameters of a = 8.725 ?, b = 8.063 ?, and c = 5.569 ?. Optical analysis of the La6Ge thin films reveal their high transparency, with an energy bandgap of 3.75±0.04 eV. The bandgap exhibits indirect allowed transitions and featured energy band tails with widths measuring (1.64±0.14) eV. In addition, dielectric dispersion analyses indicate the presence of two dominant dielectric resonance peaks centered at 3.15 and 2.08 eV. Moreover, the La6Ge films demonstrate a terahertz (THz) cutoff frequency of 1.0 THz when illuminated with infrared and visible light. This cutoff frequency increases to 45.6 THz in the ultraviolet range. Furthermore, by utilizing the Drude–Lorentz method, the investigation of optical conductivity parameters reveals that the lanthanum germanide optical filters can achieve free hole density and drift mobility values of 14.44 cm2 V?1 s?1 and 2.8×1018 cm?3, respectively, under infrared light irradiation. The outstanding optical and dielectric properties exhibited by the La6Ge thin films make them excellent candidates for highly transparent optical filters suitable for terahertz technology.Öğe Growth and characterization of PbSe microcrystals via the pulsed laser welding technique(SPRINGER HEIDELBERG, 2022) Alkhamisi, Manal M.; Khanfar, Hazem K.; Algarni, Sabah E.; Qasrawi, Atef FayezHerein lead selenide crystals are fabricated by the pulsed laser welding (PLW) technique within 2 min. The effect of the pulse width on the crystallinity, surface morphology, structural parameters, compositional stoichiometry, electric resistivity and dielectric constant is considered. It is observed that the PLW technique allowed the growth of the crystals in a short period of time. The grown PbSe crystals are mostly cubic containing tetragonal SeO2 as a minor phase. Selenium oxide presented due to the surface oxidation of PbSe after exposing the crystals to air. Remarkable decreases in the electrical resistivity and increase in the dielectric constant by more than two orders of magnitude are achieved as the pulse width increases from 10 to 50 ms. It is observed that the optimum pulse width revealing the highest dielectric constant value is 30 ms. For these samples, a negative capacitance effect is observed for ac signals of frequencies larger than 700 MHz. In addition, analyzing the microwave cut-off frequency spectra for an imposed signal of low amplitude displayed cut-off frequency values larger than 100 GHz at the point where negative capacitance dominates and ac conductance shows a maxima. The features of the PbSe crystals which are prepared in 2 min nominate them for use as negative capacitance sources and band filters suitable for 6G technologies.Öğe La/Ge stacked nanosheets designed as optical resonators, microwave oscillators and 5 G/6 G gigahertz receivers(Optik, 2023) Alkhamisi, Manal M.; Qasrawi, Atef Fayez; Khanfar, Hazem K.Glass/Ge and La/Ge stacked layers, 100 nm thick, were prepared via thermal evaporation under a vacuum pressure of 10-5 mbar. Structural analysis confirmed amorphous growth of Ge nanosheets. Optically coating Ge onto La improved light absorption, energy band gap, and dielectric responses. In addition, dielectric spectra fitting using Lorentz approach showed increased free electron density, plasmon frequency, and drift mobility (up to 1153 cm2/Vs) in Ge due to lanthanum presence. Moreover, LGA Schottky barrier devices (La/Ge/Au) exhibited tunneling-type current conduction with 0.815 eV barrier height and 40 nm width. Resistance spectra of these Schottky barriers displayed negative resistance near 0.40 GHz, while capacitance spectra showed resonance-antiresonance behavior. La/Ge and LGA interface can be utilized for optical receivers and microwave resonators in 5 G/6 G technologies.Öğe Lead selenide microcrystals fabricated by the pulsed laser welding technique employed as 6G technology microwave resonators and as MOS capacitors(Elsevier, 2023) Alkhamisi, Manal M.; Khanfar, Hazem K.; Qasrawi, Atef Fayezvalue larger than 100 GHz nominating the devices for 6G technology applications. Moreover, investigations on the current conduction mechanism have shown the preferred current conduction by quantum mechanical tunneling accompanied with correlated barrier hopping. On the other hand, measurements of the capacitance-voltage characteristics in the frequency domain of 1.0–100 MHz showed performance of the Ag/PbSe/Ag structures as a metal-oxide- semiconductors (MOS) devices suitable for energy storage at ultrashort times.Öğe Lead selenide thin films designed for laser sensing and visible light communications(Springer, 2023) Khusayfan, Najla M.; Qasrawi, Atef Fayez; Khanfar, Hazem K.; Alharbi, Seham R.Herein thin films of PbSe are coated onto amorphous glass, amorphous silicon (a?Si) and crystalline n?type Si (n?Si) wafers by the thermal evaporation technique under a vacuum pressure of 10? 5 mbar. The films are structurally, morphologically, compositionally, optically and electrically characterized. Strong effect of the nature (amorphous or crystalline) and type (Si or glass) of the substrate on the physical properties of lead selenide films is detected. Of these properties the crystallite sizes decreased and the microstrain, the stacking faults and defect density increased and the energy band gap is blue shifted when (a, n)-Si substrates replaces glass. In addition, the use of crystalline n?Si substrates instead of a?Si removed the free carrier absorption from a?Si/ p?PbSe improving the quantum efficiency of the devices. Opto-electronically, n?Si/p?PbSe films showed photosensor characteristics that suit both visible light and infrared technology applications. The photosensors displayed high current responsivity, external quantum efficiency percentages and response times reaching respective values of 1.4 A/W, 172% and 60 ?s. In addition, the n?Si/p?PbSe photosensors which were used as detectors to receive wireless light signals generated from light pulses of 10 kHz frequencies showed smart features nominating them as promising devices for laser sensing and visible light communication technology.Öğe Lead-tungsten oxide interfaces designed as gigahertz/terahertz filters(IOP Science, 2023) Alkhamisi, Manal M.; Qasrawi, Atef Fayez; Khanfar, Hazem K.Herein amorphous tungsten oxide thin films of thicknesses of 300 nmare coated onto semitransparent Pb films (100 nm) by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. Optical investigations in these films have shown that Pb nanosheets enhances the light absorbability in the visible and infrared ranges of light without significant change in the energy band gap value. In addition deep analyses of the optical conductivity and terahertz cutoff frequency spectra of the Pb/WO3 optical filters revealed that the cutoff frequency value in the visible range of light is invariant with light signal energy indicating the possibly of filtering none-monochromatic light signals. Onthe other hand imposing an ac signal between the terminals of Pb/WO3/Au devices has proofed the ability of the device to perform as low pass and as band stop filters workable in the microwave frequency domain. The microwave cutoff frequency for this device reached?9 GHz nominating it for use in 5 Gmobile technology. The current study showed that coating of tungsten oxide onto semitransparent Pb substrate and coverage small area of the top contact with Au can allÖğe Preparation and characterization of orthorhombic AgMn alloys by the pulsed laser welding technique(Wiley, 2022) Khanfar, Hazem K.; Qasrawi, Atef FayezHerein, AgMn alloys are prepared by the pulsed laser welding technique in an argon atmosphere. The effect of the laser pulses width and stoichiometric composition of the alloys on the structural, compositional, morphological, and electrical properties are investigated. In contrast to the traditional preparation techniques which reveal cubic structure of AgMn alloys, the pulsed laser welding technique reveals the orthorhombic phase of the alloys. The lattice parameters of the orthorhombic phase of AgMn are a = 13.0250 Å, b = 15.7768 Å, c = 2.6728 Å. It is observed that pulse widths of 50 ms are the optimum from preparing these alloys. From an electrical point of view, the AgMn alloys exhibit negative dielectric constant and negative conductance effect in the microwave frequency domain. The impedance spectroscopy analyses in the frequency domain of 0.01–1.80 GHz have shown that AgMn alloys can be employed as band filters with return loss value of ?16 dB. The features of the AgMn alloys which are achieved by the pulsed laser welding technique nominate them for use as negative capacitance and negative conductance transistors. These devices are suitable for noise reduction and parasitic capacitance cancellation.Öğe Pt/PbSe optoelectronic receivers designed for 6G and terahertz communication technologies(SPRINGER, 2023) Alkhamisi, M.M; Qasrawi, Atef Fayez; Khanfar, Hazem K.; Algarni, Sabah E.Herein PbSe thin films are coated onto glass and semitransparent platinum substrates. The films which are treated as optoelectronic signal receivers are deposited by the thermal evaporation technique under a vacuum pressure of 10?5 mbar. The structural investigations have shown that (glass, Pt)/PbSe films are of polycrystalline nature. Optically, Pt substrates increased the transparency and reflectivity of PbSe films. The energy band gap of PbSe is also increased by 0.12 eV when films are coated onto Pt substrates. In addition the dielectric constant also increased as a result of strong interaction between Pt plasmonic particles and lead selenide. On the other hand, fitting of the imaginary part of the dielectric constant using Drude–Lorentz model has shown that coating of PbSe onto semitransparent Pt substrates increased the drift mobility of lead selenide by four times. Pt substrates resulted in a decrease in the density of free charge carriers and increases the scattering time constant at femtosecond levels. (Glass, Pt)/PbSe optoelectronic receivers displayed plasmon frequencies up to?~?13 GHz and showed terahertz cutoff frequency of?~?1.0 THz. In addition, allowing the propagation of an ac signal of low amplitude in the Pt/PbSe/Pt receivers has shown that the devices exhibit wide range of resistance tunability. The microwave cutoff frequency also reached 14 GHz. Both of the optical and electrical measurements proved the suitability of the Pt/PbSe devices for 6G and terahertz communication technologies.Öğe Voltage and frequency controlled Ge/SeO2 thin film transistors designed as rectifiers, negative capacitance and negative conductance sources(Virtual Co. Physics SRL., 2023) Qasrawi, Atef Fayez; Khanfar, Hazem K.Herein voltage and frequency controlled thin film transistors fabricated by depositing SeO2 onto germanium thin crystals are reported. For these devices measurements of the current-voltage characteristics revealed a biasing dependent rectification ratios. The devices showed metal-oxide-semiconductor character under reverse biasing conditions. In addition, the biasing dependent capacitance and conductance spectral studies in the frequency domain of 20M-1000MHz has shown the possibility of switching the capacitance and negative conductance from negative mode to positive mode. The features of the Ge/SeO2 devices make them attractive for use in electronic circuits as parasitic capacitive circuit elements, noise reducers, signal amplifiers and microwave oscillators.
